One of the important operational requirements of networks is to provide uninterrupted service in the face of failures. This is usually known as network survivability or network resilience, and network service providers consider this requirement to be one of the key requirements that is usually demanded by customers. Depending on the type of the network, and the technology employed therein, failures may be more frequent, and even more catastrophic for one type of networks as compared to other types of networks. For example, in networks implemented with optical fibers as the physical transmission medium, large amounts of bandwidth are provided on a single wavelength channel, and huge amounts of traffic are carried on the fiber, especially if dense wavelength division multiplexing (DWDM) is used. Fibers, however, can be damaged accidentally with a probability that is much higher than the damage probability for other types of physical media. The failure of a single fiber, which is not uncommon, can therefore affect a large number of users and connections. Hence, it is very important to provide a high degree of survivable network operation in the face of failures in optical communication networks.
A large number of techniques for providing optical network survivability have been introduced. Such techniques can be classified as either Predesigned Protection, or Dynamic Restoration techniques (D. Zhou and S. Subramaniam, “Survivability in optical networks,” IEEE Network, vol. 14, pp. 16-23, November/December 2000). In predesigned protection, which is a proactive technique, bandwidth is reserved in advance so that when a failure takes place, backup paths which are pre-provisioned, are used to reroute the traffic affected by the failure. These techniques include the 1+1 protection, in which traffic of a lightpath is transmitted on two link disjoint paths, and the receiver selects the stronger of the two signals; 1:1 protection, which is similar to 1+1, except that traffic is not transmitted on the backup path until failure takes place; and 1:N protection, which is similar to 1:1, except that one path is used to protect N paths. A generalization of 1:N is the M:N, where M protection paths are used to protect N working paths. Protection techniques are widely used in SONET ring networks (D. Zhou and S. Subramaniam, “Survivability in optical networks,” IEEE Network, vol. 14, pp. 16-23, November/December 2000). Under dynamic restoration, which is a reactive strategy, capacity is not reserved in advance, but when a failure occurs spare capacity is discovered and is used to reroute the traffic affected by the failure. Protection techniques can recover from failures quickly, but require significant amounts of resources. On the other hand, restoration techniques are more cost efficient, but are much slower than their protection counterparts.
The concept of p-Cycles was recently introduced to emulate the protection techniques of SONET ring networks, and they provide 1:N protection to connections with the same transport capacity, e.g., DS-3. p-Cycles provide protection against single link failures to a connection with its two end nodes being on the cycle. However, under p-Cycles, and because of the shared protection, failures must still be detected, and traffic must be rerouted on the cycle. (D. Stamatelakis and W. D. Grover, “Theoretical underpinnings for the efficiency of restorable networks using preconfigured cycles (p-cycles),” IEEE Transactions on Communications, vol. 48, no. 8, pp. 1262-1265, 2000; D. Stamatelakis and W. D. Grover, “Ip layer restoration and network planning based on virtual protection cycles,” IEEE Journal on Selected Areas in Communications, vol. 18, no. 10, pp. 1938-1949, 2000; and W. D. Grover, Mesh-based survivable networks: options and strategies for optical, MPLS, SONET, and ATM Networking. Upper Saddle River, N.J.: Prentice-Hall, 2004).
Recently, one of the present inventors introduced another new concept for protection, namely, 1+N protection described in U.S. Provisional Patent Application No. 60/990,183, filed Nov. 26, 2007, herein incorporated by reference in its entirety. The technique is based on using a bidirectional p-Cycle to protect a number of link disjoint connections which are straddling from the cycle, and using network coding (R. Ahlswede, N. Cai, S.-Y. R. Li, and R. W. Yeung, “Network information flow,” IEEE Transactions on Information Theory, vol. 46, pp. 1204-1216, July 2000) to transmit modulo-2 sums of the connections' signals on the cycle. A failure of any link on a working path can be recovered from by using a decoding operation of the signals transmitted on the p-Cycle. This strategy was introduced to provide 100 percent protection against single link failures. The 1+N protection can be implemented at a number of layers, and using a number of protocols.
Despite advancements in the field, problems remain. Therefore, it is a primary objective of the present invention to provide network protection.
It is a further object, feature, or advantage of the present invention to reduce the amount of resources needed to provide network protection.
It is also an objective, feature, or advantage to recover from the failure as fast as possible, and without invoking management and control plane functionalities.
Yet another object, feature, or advantage of the present invention is to reduce the costs and effects of failures on a network by providing network protection.
One or more of these and/or other objects, features, or advantages of the present invention will become apparent from the specification and claims that follow.